What Is AJAX (Asynchronous JavaScript and XML)? Meaning, Working, and Applications

Asynchronous JavaScript and XML (AJAX) is defined as a programmatic approach used to develop highly interactive and responsive web applications by exploiting a set of technologies.Â
This article explains the core principles and workflow of AJAX.

What Is AJAX?
How Does AJAX Work?
Applications of AJAX

What Is AJAX?

Asynchronous JavaScript and XML (AJAX) develops highly interactive and responsive web applications by exploiting a set of technologies. It allows developers to update individual web page components in real time without reloading the entire webpage.

Before AJAX, whenever a part of webpage content needed to be changed or altered, the process would reload and refresh the whole webpage from the web server. The result of such a method was that it would create large portions of duplicated data in every instance. This problem was resolved with the introduction of AJAX, which allowed web parts to be updated asynchronously without reloading the entire page. This method ensured that updates were displayed almost instantaneously to end users.

AJAX relies on the following technologies to carry out smooth data interchange between a browser and web server:

- XHTML and CSS: Data presentation
- HTML Document Object Model (DOM): Enable dynamic user interaction while displaying the updated content
- XMLHttpRequest object: Move, manipulate, and update data to and from the server
- XML, HTML, XSLT, and JSON: Manage data exchange with the server
- JavaScript: Couple data requests with the content display on the user side

The combination of these technologies is crucial in establishing seamless client-server communication without page reloads. As a result, users can interact better with the web application as this method can reload partial updates. Moreover, the technique gives users the power to control their computing environment, much like in traditional desktop applications.

Additionally, while the web server processes the necessary updates on webpages, users can continue to interact with the web application, unlike traditional applications where user interaction is stalled until the HTTP transport to and from the server is complete.

Webpage content can be updated using AJAX in the following scenarios:

1. User-initiated events: For instance, if a user clicks on a specific button or hovers over a specific text, AJAX can come into action.
2. Predefined time intervals: In some cases, updates may be scheduled every 10 seconds.
3. Application logic: If the user selects the drop-down menu that shows the top 100 US universities, AJAX can subsequently load and update the list of applicable US universities based on current rankings.

It is worthwhile to note that since AJAX is not reliant on web servers, it exercises a data-driven approach rather than the conventional page-driven technique. Consequently, the procedure can execute jobs in an asynchronous manner at any time. Owing to this ability to perform partial tasks independently, several browsers today, such as Mozilla Firefox (version 1.0 and above), Apple Safari (version 1.2 and above), Chrome, Microsoft Internet Explorer (version 5 and above), and Opera (version 7.6 and above) support AJAX technology.

Key benefits of AJAX

AJAX renders several benefits to web applications, such as:

1. AJAX is a type of web browser technology that is based on open standards. It uses JavaScript libraries such as Dojo toolkits to enable AJAX applications that function across multiple browsers.
2. AJAX applications work on browsers without the need for any additional software plugins.
3. AJAX is used by several ecommerce companies, such as Shopify and online platforms, to enable intuitive user interactions. Ecommerce features such as listing products, adding products to a shopping cart, or streamlining the checkout process, such as one for Shopify, are all enabled by AJAX.
4. AJAX is similar to Web 2.0 applications that use a group of technologies, collaborative applications, and knowledge sources, such as blogs, forums, and so on, to build the next generation of the internet.
5. AJAX keeps a check on server traffic since server communication happens only for â€˜bits of web content.’
6. AJAX technology consumes less bandwidth, thanks to the principle of fetching only small packets of data from the server.
7. AJAX improves overall user experience while interacting with web applications.

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How Does AJAX Work?

In a conventional web application, the browser directly communicates with the server. The server responds by sending all the HTML and CSS code at once. Further, if the user makes another request from the webpage, then the server processes the new user data, performs the task of rebuilding the page, and then sends the newly built webpage to the user.

With AJAX, the webpage is loaded just once when the user makes the initial request. In case of any further user requests on a webpage, the AJAX engine captures the user data for the small segment of the webpage that needs to be updated and sends the request to the web server. The server then responds asynchronously by processing the requested content without interfering with the display and behavior of the existing webpage.

While this reveals the working of a simple AJAX application, let’s dive into the technical steps involved in processing the AJAX requests. The workflow of AJAX begins with the browser reaching out to the server via the XMLHttpRequest object. The process follows a series of steps, as shown below:

- Step 1: First, the user instantiates the HTTP request via the user interface. This results in a JavaScript call forwarded to the JavaScript interpreter, also referred to as the AJAX engine, residing in the web browser.
- Step 2: In the second step, the AJAX engine sends the corresponding HTTP request via the XMLHttpRequest object to the web server.
- Step 3: Next, the web server connects to the underlying backend databases using JSP, ASP.net, and PHP, responsible for data handling and manipulation. Subsequently, data exchange occurs between the data store and the server, and the requested data is retrieved.
- Step 4: Next, the web server sends back the retrieved HTML, XML, or JavaScript data to the AJAX engine, also referred to as the XMLHttpRequest callback function.
- Step 5: Lastly, the JavaScript interpreter displays the HTML and CSS content on the UI of the browser.

In the AJAX environment, the developer is responsible for writing codes that not only make requests to the web server but also deal with the response. However, in a normal HTTP request, both these aspects are taken care of by the browser, and the developer is not held accountable for managing codes that initiate requests and handle responses to and from the server, respectively.

With AJAX, the developer has control of all web page components displayed to the end user. The developer can update any part of the webpage with ease just by employing a few dynamic DOM manipulation techniques that do not need the reloading of the entire page. All the updates happen in the background. Thus, AJAX works on the principle of â€˜refresh without reload.’Â Â

Moreover, AJAX refines the traditional browser-server communication model by adding an additional functional layer in the form of an â€˜AJAX engine.’ It acts as an intermediary between the user interactions with the client-server model.

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Applications of AJAX

The demand for responsive web applications has grown substantially in recent times. Today, users have become habitual in receiving instant updates while interacting with websites. This is why AJAX principles have been at the forefront of web technology.

Let us understand some practical examples of AJAX that treat web applications much like desktop versions.

AJAX Applications

1. Instant login systems

Websites such as Digg.com use a login system where the user need not open a separate login page to access their account. Instead, the original page of the site has an option for users to directly enter their credentials (i.e., username and password). When the user data is entered, the AJAX functionality then sends the login request to the target server. The server then responds by updating the login portion. Also, the web page lets you know that you have logged into the system. From thereon, the webpages are updated based on user actions.

2. Autocomplete feature

Google was the first organization to deploy AJAX technology across its products. Google’s autocomplete feature is a good example of AJAX. As users enter search queries on the Google search bar, the feature provides suggestions in real-time without refreshing the original web page during the process.

Apart from Google search, the autocomplete feature is suitable for forms requiring many user inputs. An alternative approach of providing a drop-down list can be cumbersome in many cases, as the list can end up becoming too long for the UI.

3. Voting and rating systems

Several websites allow users to decide and customize the information on their web pages based on their votes. For example, Digg and Reddit are social bookmarking sites that offer such functionality that allows users to vote for certain content and based on those votes, the site’s main content is updated.

Such sites use AJAX features to manage and handle user votes. As a result, users’ opinions on stories and content are considered valuable, and websites can continue to fine-tune their strategies to optimize user-facing content.

4. Social media

Due to its user-friendly interface, Twitter, the social media platform, has become popular over the years. When someone tweets, it is instantly added to the user’s feed, and everything on the site gets updated. Recently, Twitter added AJAX functionality to its â€˜trending topics’ section. As a result, users receive updates every few seconds whenever new tweets are put out on trending topics. Twitter is an excellent example of how AJAX can not only update user content but also give them a hint on current user sentiments on specific topics.

5. Form submission and validation

As mentioned earlier, AJAX can be employed for form submission and validation tasks where certain fields in the form require auto-filling while others continue to give suggestions on possible entries, much like the autocomplete feature. AJAX makes form filling much easier for end users since they need not worry about typos or other critical mistakes, such as entering irrelevant texts under the salary field.

Moreover, AJAX is also used by some sites to validate the strength of user credentials such as passwords. In some cases, AJAX points out whether or not the user has entered a valid email or URL in the online form.

6. Chats and instant messages

Online chatting has evolved in leaps and bounds from what it was back in the 1980s when Internet Relay Chat (IRC) was introduced. Today, several websites, such as Amazon, use the â€˜customer support chat’ facility on their homepage. As users explore websites, they can simultaneously have a one-on-one conversation with customer service representatives without having to reload the entire webpage. This feature is a consequence of AJAX technology.

7. Simple user interfaces

AJAX is a popular tool used by developers to create simple yet efficient UIs. Such interfaces are easy to use since users can complete their tasks on one webpage. It is far more efficient than jumping from one page to another to finish a single task. This has two fundamental advantages: firstly, it makes the web application fairly quick and user-centric, and secondly, it gives better control over bandwidth and website load times since the number of user requests forwarded to the server is considerably lesser.

For example, Drop.io, an online file-sharing service, uses AJAX to enable slick user interfaces. Google has also unveiled AJAX-based applications such as Google Docs and Google Maps. The interface used by Google Maps allows users to update and change map views based on real-time user inputs.

8. Widgets

One advantage of AJAX is its ability to make a call to multiple online servers while in operation. This implies that the webpage that uses JavaScript is not restricted to its own server but can also connect to other online servers. For example, the content management system of WordPress supports several plugins that work in this manner. Another example is Google Adsense. The scripts of Adsense, too, have a similar workflow.

9. Lightboxes

Today, several websites use pop-ups for targeted advertisements. However, such pop-ups are quite problematic for users. Instead, AJAX content can be coupled with lightboxes that overlay on webpages. Until the user responds to these lightbox displays, they cannot take any further action. This is generally observed in cases where a user tries to add his opinion or review on sites without logging in or registering. As the user tries to enter text, a pop-up appears that says, â€˜you need to log in first.’ It is necessary for the user to respond to that pop-up to write a review or navigate the site. AJAX-enabled lightboxes are better suited for users than random pop-ups.

10. Flash

Flash refers to an animation toolkit used to create games, animations, and web page elements. Combining AJAX with flash further optimizes website designs. For example, Kongregate, a web gaming portal, uses flash APIs to update the profiles of players whenever they win a badge while playing an online game. As and when the player wins a reward, the flash APIs send a request to JavaScript, which uses AJAX features to update the player’s profile. The profile is thereby maintained in real-time.

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Takeaway

In summary, AJAX is a client-side script that establishes a robust communication channel between the client and server side. Traditional desktop applications lacked the ability to maintain an explicit link with servers. It was only when the page was reloaded entirely that the client-server interaction could take place. However, AJAX broke this paradigm of page reloads, which, in turn, saved a lot of bandwidth for web apps.

With AJAX ushering in a new era in web development, the technology made internet applications much faster and more user-friendly.

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